Harmonic balancing device for internal combustion engines



Dec. 3, 1963 M. J. BERLYN 3,112,658

HARMONIC BALANCING DEVICE FOR INTERNAL COMBUSTION ENGINES Filed Aug. 18, 1960 4 Sheets-Sheet 1 INVENTOR. MARTIN J. BE'ELYN A TTOP/VEK Filed Aug. 18, 1960 Dec. 3, 1963 M. J. BERLYN 3,112,658

HARMONIC BALANCING DEVICE FOR INTERNAL COMBUSTION ENGINES 4 Sheets-Sheet 2 AXIS or CEANKPINS 5 AXIS 0F CEANKPIN 9 AX [5 OF CEANKSHAFT F'Jg' .3

INVENTOR.

Dec. 3, 1963 M. J. BERLYN 3,112,658

HARMONIC BALANCIN EVICE FOR INTERNAL COMBUSTI ENGINES Filed Aug. 18, 1960 4 Sheets-Sheet 3 III ' INVENTOR.

MARTIN J. BEELYN 1963 M. J. BERLYN 58 HARMONIC BALANCING DEVICE FOR INTERNAL COMBUSTION ENGINES Filed Aug. 18, 1960 4 Sheets-Sheet 4 commecrme ROD CENTER LINE.

AXIS OF CYLINDER mmvron. MARTIN J. BEELYN} ATTUPA/EK United States Patent 3,112,658 HARMGNIC BALANCING DEVICE FUR INTERNAL CGMBUSTIGN ENGINES Martin J. Beriyn, 1650 Dorchester St. W., Montreal, Quebec, Canada Filed Aug. 18, 19530, Ser. No. 50,353 13 Ciaims. (Cl. 74-603) This invention relates to a new and improved harmonic balancing device for internal combustion engines.

An object of this invention is to provide, for compensation of primary and secondary unbalance in reciprocating engines, a harmonic balancer of inherently low power consumption.

Another object is to provide a harmonic balancer of compact form.

Another object is to provide a harmonic balancer of low cost.

Another object is to provide a harmonic balancer which will not increase the crankcase depth of vertical engines.

Another object is to provide a harmonic balancer which, as applied to parallel twin engines, does not increase the engine length.

Another object is to provide a harmonic balancer which will make practicable the commercial high-speed parallel twin engine in sizes considerably greater than heretofore.

Other objects and advantages of the invention will be apperent from the following description taken in connection with the accompanying drawings in which the preferred forms of the invention have been given by Way of illustration only.

Referring to the drawings:

FIG. 1 shows the transverse median section of a parallel twin engine incorporating the preferred execution of harmonic balancer according to this invention. As shown in FIG. 1, the crankshaft is at top dead centre position.

FIG. 2 shows a partial vertical longitudinal section in the plane of the crankshaft axis, corresponding with 22 of FIG. 1.

FIG. 3 shows a partial section along 33 of FIG. 1.

FIG. 4 shows a section in the same plane as FIG. 1 but with the crankshaft turned through 90 from dead centre.

FIG. 5 shows a horizontal section in the plane of the crankshaft axis, corresponding with 55 of FIG. 4.

FIG. 6 is a view generally similar to FIG. 4 but shows a modified form of the invention.

In single-cylinder reciprocating engines of conventional type, wherein linear motion of the piston is converted into circular motion of the crankpin by means of an intermediate connecting rod, the harmonic linear accelerations of the reciprocating masses cause unbalanced linear forces which cannot be compensated by counterweights attached to the crankshaft.

Two different devices for compensating these unbalanced linear forces have been employed up to this time. Both of these devices achieve overall engine balance by generating another system of linear forces of equal magnitude but of opposite sign. All balancers for compensating unbalanced linear forces originating in the reciprocating masses of the engine must create opposing forces acting along a straight line which passes through the centre of gravity of the reciprocating masses of the engine and which also intersects the axis of the crankshaft.

In the first device, a combination of cranks, connecting rods, and dummy pistons is used.

In the second device, two pairs of counter-rotating eccentrically-weighted shafts are used, one pair driven at crankshaft speed and the other at twice crankshaft speed.

3 ,112,658 Patented Dec. 3, 1963 In the first device, the dummy pistons must be on the opposite side of the crankshaft from the power piston, and the cranks for the dummy pistons must be phased from the power crank. This balancer has proved satisfactory in application to research engines, but it is unattractive for commercial engines and has never been so applied. The two additional cranks (which usually take the form of eccentrics) substantially increase both the length of the crankshaft and the span between crankshaft main bearings. In vertical engines, the dummy pistons must be below the crankshaft, which increases the depth of the crankcase; furthermore, the power loss due to the friction of the dummy pistons in their guides is unacceptable in commercial engines and is tolerable only in the case of research engines.

In the second device, it is not practicable to locate the two pairs of eccentrically-weighted shafts anywhere in the engine assembly other than the side of the crankshaft axis remote from the cylinder. Here again, for vertical engines, the increase of crankcase depth is intolerable and, since this balancer comprises four shafts, a minimum of nine bearings, and at least five gears, the expense is tolerable only in the case of research engines.

Up to this time there has not been offered a commercially accept-able harmonic balancer for compensating the linear primary and secondary unbalanced forces of singlecylinder reciprocating engines. Commercial acceptability, in this connection, is conditional on low power consumption, low first cost, compactness, and disposition of the balancer in vertical engines such that the crankcase depth is not increased.

P or many years, a specialized type of high-speed twocylinder four-stroke cycle engine has been widely used in motorcycles. In engines of this type the two crankpins are spaced on a common axis and the two pistons therefore move at the same speed in the same direction at all times. This arrangement is very popular because it can provide equally-spaced firing intervals in a two-cylinder four-stroke cycle engine of simple and compact configuration. In the industry, this type of engine is referred to as a parallel twin. Since the cylinder axes are parallel and the two pistons move in unison side-by-side, the parallel twin is dynamically similar to a single-cylinder engine and has only been practicable in small sizes on account of the characteristic vibration at high speeds which is intolerable in engines whose total piston displacement exceeds about 40 cubic inches.

In a single-cylinder engine, the line along which the balancer-generated forces must act is the cylinder am's itself. This is to say that with a harmonic balancer of the dummy-piston type, there must be two identical dum-my pistons symmetrically spaced from the cylinder axis. In a parallel twin, the line along which the balancer-generated forces must act lies in the median transverse plane of the engine. An attractive economy appears to be possible, in the case of the parallel twin, by location of a single dummy piston in the median transverse plane of the engine. However, in the presentlyknown dummy-piston type of harmonic balancer, the balancer cranks mus-t be phased 180 from the power crank; this is to say that a single balancer crankpin in the median transverse plane of a parallel twin would not overlap the power crankpins. In the absence of overlap, the crankshaft structure would have to include two additional crankwebs of greater axial thickness than the webs which connect the power crankpins to the main crankshaft journals. The use of a single dummy piston for the balancing of a parallel twin engine, therefore, does not in fact result in a shorter engine.

I have now invented a harmonic balancer, suitable for commercial single-cylinder and parallel twin engines, which does not increase the crankcase depth and in which there are neither crosshead-guided reciprocating counterweights nor geared pairs of shafts carrying rotary counterweights. My harmonic balancer has the further great advantage that its cranks are in phase with the power crank; substantial economy in engine length results from this characteristic when my balancer is applied in singlecrank form to the parallel twin, because the balancer crank-pin overlaps the power crankpins, permitting the use of axially thin webs for connection of the balancer crankpin to the power crankpins.

For convenience, the following description of my harmonic balancer will be referred specifically to enginesof the parallel twin type, but it will be apparent that the device is applicable also to single-cylinder engines, and to multi-cylinder engines other than the parallel twin, without departing in any way from the spirit of the invention.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout:

The major moving parts of a conventional parallel twin four-stroke cycle engine are clearly shown in P16. 2; they consist of two pistons 1 and two connecting rods 11, also crankshaft 14, which has two crankpins spaced apart on a common axis and two counterwcights 6.

The forces due to pistons 1 are transmitted to crankpins 5 by way of connecting rods :11.

In order to drive the harmonic balancer according to this invention, an additional crankpin is provided.

Crankpin 9 is located in the plane of symmetry between crankpins 5. The eccentricity of crankpin 9 from the axis of crankshaft 14 is preferably about half the eccentricity of crankpins 5.

The axes of crankshaft 14- and crankpins 5 lie in a common plane. The axis of crankpin 9 also lies in this plane intermediately of crankshaft 14 and crankpins 5.

With reference now to FIGS. 1, 2 and 5, the balancer consists of two connecting rods 3 whose inner ends are journaled side by side on crankpin 9 and whose outer ends comprise relatively massive 'bobweights 7. The two bobweights 7 are on opposite sides of crankpin 9 and are operably connected by wristpins 8 to forked links 13. Forked links 13 are operably connected to engine frame =12 by means of fulcrum pins 4.

Although bobweights 7, as a matter of manufacturing convenience, are made integral with connecting rods 3 they constitute, in combination with forked links 13, two simple pendulums.

Considering the dynamics of connecting rods 11, their upper portions may be assumed to be reciprocating in unison with pistons 1 and their lower portions may be assumed to be rotating in unison with crankpins 5. Similarly, the outer portions of connecting rods 3, wristpins S, and the lower portions of forked links 13- may be considered as parts of bobweights 7 and constrained to traverse arcuate paths having a radius equal to the distance between the axes of wristpins 8 and fulcrum pins 4. The inner portions of connecting rods 3 may be assumed to be rotating in unison with crankpin 9.

In order to construct 'a harmonic halancer in accordance with this invention so that it will compensate accurately the primary and secondary unbalanced linear forces inherent in the engine, certain equations of dimension and mass must be respected.

Where W=eifective mass of bobweights 7 w =eifective mass of pistons 1 S=stroke of pistons 1 s -'effective linear amplitude of bobweig hts 7 R=eccentricity of crankpins 5 r=eccentricity of crankpin 9 L=length of connecting rods 11 (from axis of wristpin it) to axis of crankpin 5) l=length of links 13 (from axis of fulcrum pin 4 to axis Counterweights 6 not only balance the rotating eccentric portions of crankshaft 14 and the inner ends of connecting rods 3 but also counterpoise pistons l, wristpins 10 and the Whole of connecting rods 11. This is to say, in the language of engine designers, that counterweights 6 balance the rotating masses and all of the reciprocating masses (the reciprocating masses being the pistons 1, the wristpins 1E) and the upper portions of connecting rods 11). V

Such counterweights can not, by themselves, result in a perfectly balanced vibration-free engine because those portions of them which counterpoise the reciprocating masses cause horizontal free forces. Also, crankshaft counterweights can do nothing to compensate secondary unbalance, which has a frequency twice that of crankshaft rotation.

If Equations i and ii above are observed, bobweights 7 are subjected to cyclical horizontal accelerations, at the the frequency of crankshaft rotation, which exactly oppose and cancel the horizontal components of force created by those portions of counterweights 6 which counterpoise pistons 1, wristpins 1t) and the upper portions of connecting rods 11 (see FIG. 4).

Again, if Equations i and ii are observed, bobweights 7 are subjected to cyclical vertical accelerations, at twice the frequency of crankshaft rotation, which exactly oppose and cancel the vertical secondary forces created by accelerations of the reciprocating components of the engine due to cyclical angularity of connecting rods 11 (see FIGS. 1 and 4).

It will be seen, therefore, that my harmonic balancer is a simple, compact, and inexpensive device by means of which a parallel twin engine may be made free of primary and secondary unbalance.

Furthermore, it maybe seen that my harmonic 'balancer is characterized by low relative velocities of conjugate working parts and by a general arrangement of the components such as to demand no additional depth of crankcase below the crankshaft axis.

From the foregoing it will be seen that I have provided new and improved means for obtaining all of the objects and advantages of my invention.

I claim:

1. In an internal combustion engine having an engine frame, a cylinder in said frame, a piston in said cylinder, a crankshaft, a main connecting rod connecting said piston and said crankshaft, counterweights fixed to said crankshaft and rotating therewith, pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and auxiliary connecting rods connecting said pendulums to said crankshaft and means on said crankshaft operatively connected to said auxiliary connecting rods for driving said pendulums.

2. In an internal combustion engine having an engine frame, a cylinder in said frame, a piston in said cylinder, 21 crankshaft including journals and a crankpin, a main connecting rod connecting said piston and said crankshaft, counterweights fixed to said crankshaft and rotating therewith, pendulu-m supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and auxiliary connecting rods connect ing said pendulum-s to said crankshaft and means on said crankshaft operatively connected to said auxiliary connecting rods for driving said pendulurns, the axis of said means for driving said pendulums being intermediate the axis of the crank journals and the axis of said crankpin.

3; In an internal combustion engine having an engine frame, a cylinder in said frame, a piston in said cylinder, a crankshaft, a main connecting rod connecting said piston and said crankshaft, counterweights fixed to said crankshaft and rotating therewith, pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and auxiliary connecting rods connecting said pendlums to said crankshaft and means on said crankshaft operatively connected to smd auxiliary connecting rods for driving said pendulums, said pendulums each including a pivoted link pivotally connected to sm'd pendulum supporting means and to said auxiliary conn cting rods.

In an internal combustion en ine having an engine frame, a pair of cylinders in said frame, a piston in each of said cylinders, a crankshaft, a main connecting rod connecting each of said pistons and said crankshaft, counterweights fixed to and rotating with said crankshaft, pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supportinn means and on opposite sides of said crankshaft and adapted to swing in planes parallel with the planes of rotation of said countenweights and auxiliary connecting rods connecting each of said pendulums with said crankshaft.

5. in an internal combustion engine having an engine frame, a pair of cylinders in said frame, a piston in each of said cylinders, a crankshaft, a main conn cting rod connecting each of said pistons and said crankshaft, counterweights fixed to and rotating with said crankshaft, pendulum supporting means carried by said engine frame, pendulurns pivotally connected to said pendulum supporting means and on opposite sides of said crankshaft and adapted to swing in planes parall l with the planes of rotation of said counterweights and auxilia connecting rods connecting each of said pendulums with said crankshaft.

6. In an internal combustion engine having an engine frame, a pair of cylinders in said frame, a piston in each of said cylinders, a crankshaft, a main connecting rod connecting each of said pistons and said crankshaft, counterweights fixed to and rotating with said crankshaft, pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and on opposite sides of said crankshaft and adapted to swing in planes parallel with the planes of rotation of said counterweights and auxiliary connecting rods connecting each of said pendulums with said crankshaft, the pivots for said pendulums being on the same side of the crankshaft axis as the engine cylinders.

7. In an internal combustion engine having an engine frame and having a cylinder in said frame, a piston in said cylinder, a crankshaft and a main connecting rod connecting said piston and said crankshaft and counterweights fixed to said crankshaft and rotating therewith, the provision of pendulum supporting means carried by said engine frame, pendulurns pivotally connected to said pendulum supporting means and auxiliary connecting rods connecting said pendulums to said crankshaft and means on the crankshaft operatively connected to said auxiliary connecting rods for driving said pendulums.

8. In an internal combustion engine having an engine frame and having a cylinder in said frame, a piston in said cylinder, a crankshaft including journals and a crankpin, a main connecting rod connecting said piston to said crankshaft and counterweights fixed to said crankshaft and rotating therewith, the provision of pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and auxiliary connecting rods connecting said pendulums to said crankshaft and means on the crankshaft operatively connected to said auxiliary connecting rods for driving said pendulums, the axis of said means for driving said pendulums being intermediate the axis of the crank journals and the axis of said crankpin.

9. In an internal combustion engine having an engine frame and having a cylinder in said frame, a piston in said cylinder, a crankshaft and a main connecting rod connecting said piston to said crankshaft and counterweights fixed to said crankshaft and rotating therewith, the provision of pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and auxiliary connecting rods connecting said pendul-urns to said crankshaft and means on the crank-shaft operatively connected to said auxiliary connecting rods for driving said pendulums, said pendulums each including a pivoted link pivotally connected to said pendulum supporting means and to the auxiliary connecting rods.

16. in an internal combustion engine having an engine frame and having a cylinder in said frame, a piston in said cylinder, at crankshaft including journals and a main crankpin, a main connecting rod connecting said piston to said crankshaft and counterweights fixed to said crankshaft and rotating therewith, the provision of pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and auxiliary connecting rods connecting said pendulums to said crankshaft and an auxiliary crankpin on the crankshaft for driving said pendulums, the axis of said auxiliary crankpin being intermediate the axis of the crank journals and the axis of the main crankpin, said pendulurns each including a pivoted link pivotally connected to said pendulum supporting means and to said auxiliary connectiru rods.

11. in an internal combustion engine having an engine frame and having a pair of cylinders in said frame and a piston in each cylinder and a crankshaft including journals and a orankpin, a main connecting rod connecting each of said pistons to said crankshaft and counterweights fixed to and rotating with said crankshaft, the provision of pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and on opposite sides of said crankshaft and adapted to swing in planes parallel to the planes of rotation of said counterweights and auxiliary connecting rods connecting each of said pendulums with said crankshaft.

12. In an internal combustion engine having an engine frame and having a pair of cylinders in said frame and a piston in each cylinder and a crankshaft and a main connecting rod connecting each of said pistons to said crankshaft and counterweights fixed to and rotating With said crankshaft, the provision of pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and on opposite sides of said crankshaft and adapted [to swing in planes parallel to the planes of rotation of said counter- Weights and auxiliary connecting rods connecting each of said pendulurns with said crankshaft.

13. in an internal combustion engine having an engine frame and having a pair of cylinders in said frame and a piston in each cylinder and a crankshaft and a main connecting rod connecting each of said pistons to said crankshaft and counterweights fixed to and rotating with said crankshaft, the provision of pendulum supporting means carried by said engine frame, pendulums pivotally connected to said pendulum supporting means and on opposite sides of said crankshaft and adapted to swing in planes parallel to the planes of rotation of said counter- Weights and auxiliary connecting rods connecting each of said pendulurns with said crankshaft, the pivots for said pendulums being on the same side of the crankshaft axis as the engine cylinders.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Ser. No. 372,870, Eberhard (A.P.C.), published June 1, 1943. 

1. IN AN INTERNAL COMBUSTION ENGINE HAVING AN ENGINE FRAME, A CYLINDER IN SAID FRAME, A PISTON IN SAID CYLINDER, A CRANKSHAFT, A MAIN CONNECTING ROD CONNECTING SAID PISTON AND SAID CRANKSHAFT, COUNTERWEIGHTS FIXED TO SAID CRANKSHAFT AND ROTATING THEREWITH, PENDULUM SUPPORTING MEANS CARRIED BY SAID ENGINE FRAME, PENDULUMS PIVOTALLY CONNECTED TO SAID PENDULUM SUPPORTING MEANS AND AUXILIARY CONNECTING RODS CONNECTING SAID PENDULUMS TO SAID CRANKSHAFT AND MEANS ON SAID CRANKSHAFT OPERATIVELY CONNECTED TO SAID AUXILIARY CONNECTING RODS FOR DRIVING SAID PENDULUMS. 